1. Field of the Invention
The present invention relates to sensors using electromagnetic energy to detect objects within a detection zone. More particularly, the invention relates to a pill count sensor for use with an automatic medicament dispensing machine, wherein the sensor uses visible red light to detect and count pills and other medicaments such as, tablets and capsules as the pills pass through a pill detection zone. The sensor is further operable to automatically self-calibrate in order to compensate for changing light or other operating conditions.
2. Description of Prior Art
In an effort to improve efficiency, accuracy, and profitability, pharmacies increasingly use automatic medicament dispensing machines to fill prescriptions. Such dispensing machines typically use diffuse reflective infrared photoelectric (DRIP) sensors to count pills, tablets, capsules, or other countable medicaments as each prescription is being filled. Unfortunately, DRIP sensors suffer from several distinct disadvantages, including maintenance problems and inaccuracy. Additionally, DRIP sensors must be cleaned daily to remove foreign matter that might otherwise adversely affect performance.
Maintenance problems arise during initial installation and periodic calibration. DRIP sensors must be modified during initial installation to make them suitable for use with automatic medicament dispensing machines. DRIP sensors are photoelectric-type sensors that function by detecting reflected light, and each broadly comprises an infrared energy emitting lens and an infrared energy receiving lens. In order to increase calibration accuracy, a DRIP sensor must be permanently modified by installing a blocking slit plate on its emitting lens to adjust its sensitivity. However, due to manufacturing variations, the sensor is occasionally rendered insufficiently sensitive by installation of the slit plate. The resulting flawed sensor cannot be returned to the provider for replacement because of the permanent modification, yet cannot be used to count pills, and is thus discarded, thereby increasing overall production cost of the automatic medicament dispensing machine.
DRIP sensors must also be periodically calibrated in order to assure peak performance. Such periodic calibration may be required due to a number of factors, including component aging; temperature variations; power supply voltage fluctuations; and potentiometer drift. Drip sensors are calibrated by mechanical potentiometers. If a DRIP sensor is not calibrated accurately, count inaccuracy or erratic behavior can result; therefore, such calibrations must be performed by a qualified maintenance technician.
Inaccuracy is another disadvantage encountered when using DRIP sensors. As mentioned, DRIP sensors are diffuse reflective-type sensors that operate by detecting reflected energy. The sensors cannot distinguish between energy reflected from pills of interest and energy reflected from other reflective surfaces within the sensor""s sensing range. It is therefore often necessary to add matte black material, such as tape or labels, to the dispensing machine to prevent background reflection problems. In addition to adding such material, it is often necessary to calibrate the sensors to operate at a lower sensitivity to prevent sensing and locking onto energy reflected from extraneous background objects or surfaces. When calibrated to operate at a lower sensitivity, the sensors are sometimes unable to accurately count some small pills.
As stated above, DRIP sensors function by emitting infrared energy and measuring any such energy reflected from pills. Unfortunately, some pills are of a color or a texture or have other physical characteristics such that they do not sufficiently reflect infrared or other electromagnetic energy, often resulting in inaccurate counts.
Another disadvantage of DRIP sensors is their tendency to generate false readings in the presence of electric fields, such as the fields encountered during European Electro Magnetic Compliance testing.
Accordingly, there is a need for an improved pill count sensor for use with an automatic medicament dispensing machine that overcomes the limitations of the prior art.
The present invention overcomes the above-identified problems and disadvantages and provides a distinct advance in the art of pill counting sensors. More particularly, the present invention provides a pill count sensor for use with an automatic medicament dispensing machine, wherein the sensor uses electromagnetic energy, preferably visible red light, to detect and count pills and other medicaments such as, tablets and capsules as the pills pass through a pill detection zone. The sensor is further operable to automatically self-calibrate in order to compensate for changing light or other operating conditions so as to ensure continued accuracy. The preferred sensor is carried on a vial gripping mechanism and broadly comprises a light emitting array and a light receiving array, with a pill detection zone defined therebetween; a sensor amplifier; a control board interfaced with a computing device; and interconnecting cabling. The light emitting and receiving arrays emit and receive, respectively, visible red light across the pill detection zone such that any pill entering the pill detection zone is detected by a resulting disruption in received light at the receiving array. The sensor amplifier is operable to automatically self-calibrate in order to compensate for detected light levels, and to generate a pill sense signal in response to a detected pill. The control board is operable to increment a pill counter, and is interfaced with a computing device operable to report the pill count as determined by the pill counter. The pill counter may be located internally or externally to the control board. The interconnecting cabling operatively interconnects all components using fiber optic and electrical cabling.
In use, when the automatic medicament dispensing machine receives a prescription corresponding to a quantity of pills, the receiving array is moved into position by operation of the vial gripping mechanism. The sensor amplifier automatically calibrates itself to the light level the receiving array receives, with no pill in the pill detection zone. As a pill passes through the pill detection zone, the emitted light is briefly blocked, causing the receiving array to generate a lower light level signal to the sensor amplifier. The sensor amplifier detects the lower light level signal and generates a pill sense signal to the control board. The control board increments the pill counter and so informs the computing device. This process is continued until the proper amount of pills have been dispensed and counted.
These and other important features of the present invention are more fully described in the section titled DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT, below.